On Firefox:

• Go to https://he.wikipedia.org/wiki/%D7%98%D7%95%D7%95%D7%A8%D7%A7
• Expand video
• Click around the volume control

GIF of error:

Error:
https://logstash.wikimedia.org/app/kibana#/doc/logstash-*/logstash-2020.09.02/clienterror?id=AXRP9ltwNoG2jwpwrR91&_g=h@af9206a

In Safari a similar error occurs when using the volume controls on:
https://ca.wikipedia.org/wiki/Viola_d%27arc

This error appears as TypeError: undefined is not an object (evaluating 'closestHandle.addClass'):
https://logstash.wikimedia.org/app/kibana#/doc/logstash-*/logstash-2020.09.01/clienterror/?id=AXRLYeFtMQ_08tQalmPM